I have been dealing with this similar issue. We did the upgrade and ran into a couple of bugs on the mitel side. One during the actual upgrade which we worked around. Second we found that or assumed that there was something wrong with the upgrade path/install for the client.
None of our clients could make any calls. The quick fix for this was to (we have windows 7) exit UCA, go into the users profile and the roaming folder, right click on the UC folder and send to zip folder. Once the zip file was created, delete the UC folder. Then reopen the UCA client. It will prompt for login again and create a new UC folder. One downside here is that they lose their contacts. So for some I would go into uc.zip and grab the two contacts file and then replace the new ones with these. Most of the time worked. Anyway's, 90% of my clients started to work fine after that. Reports I would get back would be the client is snappier, clearer calls, just better overall.
Now for the other 10%, the fix would work, but next day when come into work and boot up their laptop, same issue. I even tried complete uninstall, delete mitel folders and start over, but everyday, the problem would come back.
I worked with out vendor who had to get with Mitel support on this. Mitel support felt it was probably a DTMF issue where digits are not seen and that there is a new SP that was released for this.
I use a virtual MAS, so shelled into it and did an update which drops the server for 10/12 mins or so. After that, everyone got another update on their client, but if fixed all but one. I only now have one user with this issue.
So try both of those or before having everyone delete their UC folder, first try getting the update. It only updates UCA as it does fix some other items as well they said.
Let me know if it helps, I am curious...
